No abstract

ObjectiveAs the current therapeutic strategies for human hepatocellular carcinoma (HCC) have been proven to have limited effectiveness, immunotherapy becomes a compelling way to tackle the disease. We aim to provide humanised mouse (humice) models for the understanding of the interaction between human cancer and immune system, particularly for human-specific drug testing.DesignPatient-derived xenograft tumours are established with type I human leucocyte antigen matched human immune system in NOD-scid Il2rg−/− (NSG) mice. The longitudinal changes of the tumour and immune responses as well as the efficacy of immune checkpoint inhibitors are investigated.ResultsSimilar to the clinical outcomes, the human immune system in our model is educated by the tumour and exhibits exhaustion phenotypes such as a significant declination of leucocyte numbers, upregulation of exhaustion markers and decreased the production of human proinflammatory cytokines. Notably, cytotoxic immune cells decreased more rapidly compared with other cell types. Tumour infiltrated T cells have much higher expression of exhaustion markers and lower cytokine production compared with peripheral T cells. In addition, tumour-associated macrophages and myeloid-derived suppressor cells are found to be highly enriched in the tumour microenvironment. Interestingly, the tumour also changes gene expression profiles in response to immune responses by upregulating immune checkpoint ligands. Most importantly, in contrast to the NSG model, our model demonstrates both therapeutic and side effects of immune checkpoint inhibitors pembrolizumab and ipilimumab.ConclusionsOur work provides a model for immune-oncology study and a useful parallel-to-human platform for anti-HCC drug testing, especially immunotherapy.

Protein Tyrosine Phosphatase, Receptor Type G (PTPRG) was identified as a candidate tumor suppressor gene in nasopharyngeal carcinoma (NPC). PTPRG induces significant in vivo tumor suppression in NPC. We identified EGFR as a PTPRG potential interacting partner and examined this interaction. Dephosphorylation of EGFR at EGFR-Y1068 and -Y1086 sites inactivated the PI3K/Akt signaling cascade and subsequent down-regulation of downstream pro-angiogenic and -invasive proteins (VEGF, IL6, and IL8) and suppressed tumor cell proliferation, angiogenesis, and invasion. The effect of Akt inhibition in NPC cells was further validated by Akt knockdown experiments in the PTPRG-down-regulated NPC cell lines. Our results suggested that inhibition of Akt in NPC cells induces tumor suppression at both the in vitro and in vivo levels, and also importantly, in vivo metastasis. In conclusion, we confirmed the vital role of PTPRG in inhibiting Akt signaling with the resultant suppression of in vivo tumorigenesis and metastasis.

NF-κB is a well-characterized transcription factor, widely known as a key player in tumor-derived inflammation and cancer development. Herein, we present the functional and molecular relevance of the canonical NF-κB p65 subunit in nasopharyngeal carcinoma (NPC). Loss- and gain-of-function approaches were utilized to reveal the functional characteristics of p65 in propagating tumor growth, tumor-associated angiogenesis, and epithelial-to-mesenchymal transition in NPC cells. Extracellular inflammatory stimuli are critical factors that trigger the NF-κB p65 signaling; hence, we investigated the components of the tumor microenvironment that might potentially influence the p65 signaling pathway. This led to the identification of an extracellular matrix (ECM) protein that was previously reported as a candidate tumor suppressor in NPC. Our studies on the Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) protein provides substantial evidence that it can modulate the p65 transcriptional activity. Re-expression of LTBP2 elicits tumor suppressive effects that parallel the inactivation of p65 in NPC cells. LTBP2 was able to reduce phosphorylation of p65 at Serine 536, inhibit nuclear localization of active phosphorylated p65, and impair the p65 DNA-binding ability. This results in a consequential down-regulation of p65-related gene expression. Therefore, the data suggest that the overall up-regulation of p65 expression and the loss of this candidate ECM tumor suppressor are milestone events contributing to NPC development.

Nuclear localization of DNAJB6 is associated with longer survival times of patients with ESCC. DNAJB6a reduces AKT signaling, and DNAJB6 expression in cancer cells reduces their proliferation and growth of xenograft tumors in mice. DNAJB6a might be developed as a biomarker for progression of ESCC.

Background and Aims Hypoxia is one of the central players in shaping the immune context of the tumor microenvironment (TME). However, the complex interplay between immune cell infiltrates within the hypoxic TME of HCC remains to be elucidated. Approach and Results We analyzed the immune landscapes of hypoxia‐low and hypoxia‐high tumor regions using cytometry by time of light, immunohistochemistry, and transcriptomic analyses. The mechanisms of immunosuppression in immune subsets of interest were further explored using in vitro hypoxia assays. Regulatory T cells (Tregs) and a number of immunosuppressive myeloid subsets, including M2 macrophages and human leukocyte antigen–DR isotype (HLA‐DRlo) type 2 conventional dendritic cell (cDC2), were found to be significantly enriched in hypoxia‐high tumor regions. On the other hand, the abundance of active granzyme Bhi PD‐1lo CD8+ T cells in hypoxia‐low tumor regions implied a relatively active immune landscape compared with hypoxia‐high regions. The up‐regulation of cancer‐associated genes in the tumor tissues and immunosuppressive genes in the tumor‐infiltrating leukocytes supported a highly pro‐tumorigenic network in hypoxic HCC. Chemokine genes such as CCL20 (C‐C motif chemokine ligand 20) and CXCL5 (C‐X‐C motif chemokine ligand 5) were associated with recruitment of both Tregs and HLA‐DRlo cDC2 to hypoxia‐high microenvironments. The interaction between Tregs and cDC2 under a hypoxic TME resulted in a loss of antigen‐presenting HLA‐DR on cDC2. Conclusions We uncovered the unique immunosuppressive landscapes and identified key immune subsets enriched in hypoxic HCC. In particular, we identified a potential Treg‐mediated immunosuppression through interaction with a cDC2 subset in HCC that could be exploited for immunotherapies.

The most frequent chromosomal structural loss in hepatocellular carcinoma (HCC) is of the short arm of chromosome 8 (8p). Genes on the remaining homologous chromosome, however, are not recurrently mutated, and the identity of key 8p tumor-suppressor genes (TSG) is unknown. In this work, analysis of minimal commonly deleted 8p segments to identify candidate TSG implicated GATA4, a master transcription factor driver of hepatocyte epithelial lineage fate. In a murine model, liver-conditional deletion of 1 Gata4 allele to model the haploinsufficiency seen in HCC produced enlarged livers with a gene expression profile of persistent precursor proliferation and failed hepatocyte epithelial differentiation. HCC mimicked this gene expression profile, even in cases that were morphologically classified as well differentiated. HCC with intact chromosome 8p also featured GATA4 loss of function via GATA4 germline mutations that abrogated GATA4 interactions with a coactivator, MED12, or by inactivating mutations directly in GATA4 coactivators, including ARID1A. GATA4 reintroduction into GATA4-haploinsufficient HCC cells or ARID1A reintroduction into ARID1A-mutant/GATA4-intact HCC cells activated hundreds of hepatocyte genes and quenched the proliferative precursor program. Thus, disruption of GATA4-mediated transactivation in HCC suppresses hepatocyte epithelial differentiation to sustain replicative precursor phenotype.

NF‐κB is a key regulator of inflammatory response and is frequently activated in human cancer including the undifferentiated nasopharyngeal carcinoma (NPC), which is common in Southern China including Hong Kong. Activation of NF‐κB is common in NPC and may contribute to NPC development. The role of NF‐κB activation in immortalization of nasopharyngeal epithelial (NPE) cells, which may represent an early event in NPC pathogenesis, is unknown. Examination of NF‐κB activation in immortalization of NPE cells is of particular interest as the site of NPC is often heavily infiltrated with inflammatory cellular components. We found that constitutive activation of NF‐κB signaling is a common phenotype in telomerase‐immortalized NPE cell lines. Our results suggest that NF‐κB activation promotes the growth of telomerase‐immortalized NPE cells, and suppression of NF‐κB activity inhibits their proliferation. Furthermore, we observed upregulation of c‐Myc, IL‐6 and Bmi‐1 in our immortalized NPE cells. Inhibition of NF‐κB downregulated expression of c‐Myc, IL‐6 and Bmi‐1, suggesting that they are downstream events of NF‐κB activation in immortalized NPE cells. We further delineated that EGFR/MEK/ERK/IKK/mTORC1 is the key upstream pathway of NF‐κB activation in immortalized NPE cells. Elucidation of events underlying immortalization of NPE cells may provide insights into early events in pathogenesis of NPC. The identification of NF‐κB activation and elucidation of its activation mechanism in immortalized NPE cells may reveal novel therapeutic targets for treatment and prevention of NPC.